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Development and Applications of Surface-Confined Transition Metal Complexes: Heterogeneous Catalysis and Anisotropic Particle Surfaces
Stockholm University, Faculty of Science, Department of Organic Chemistry. (JEB)
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The main focus of this thesis has been directed towards developing novel surface-confined transition metal complexes for applications in heterogeneous catalysis and for the preparation of anisotropic particle surfaces. The first part describes the heterogenization of a homogeneous transition metal-based catalyst tetraphenyl cobalt porphyrin (CoTPP) on silicon wafers and on silica particles. The activity in hydroquinone oxidation for the silica particle-immobilized CoTPPs was found to be increased 100-fold compared to its homogeneous congener whereas the silicon wafer-immobilized CoTPPs achieved lower activity due to the formation of clusters of catalyst molecules on the support surface as detected with atomic force microscopy (AFM). The second part of this thesis describes the development and characterization of anisotropic particle-surfaces by electrochemical site-specific oxidation of surface-confined thiols. Reactive patches or gold gradients could be obtained on the particle surfaces depending on the type of working electrode used and on the electrolyte composition. The particle surface functionalities were characterized with X-ray photoelectron spectroscopy (XPS) and the particle-surface-confined patches and gradients were conjugated with proteins to obtain fluorescence for investigation using fluorescence microscopy. Gold-functionalized siliceous mesocellular foams were further demonstrated to be highly efficient and selective catalysts in the cycloisomerization of 4-alkynoic acids to lactones. The final part of this thesis describes the preparation and characterization of palladium nanoparticles heterogenized in the pores of siliceous mesocellular foam. The nanoparticles were analyzed with transmission electron microscopy (TEM) and found to have a size of 1-2 nm. Primary- and secondary benzylic- and allylic alcohols were oxidized by the heterogeneous palladium nanoparticles in high to excellent yields using air atmosphere as the oxygen source. The nanopalladium catalyst was used up to five times without any decrease in activity and the size of the nanoparticles was retained according to TEM.

Place, publisher, year, edition, pages
Stockholm: Department of Organic Chemistry, Stockholm University , 2013. , 93 p.
Keyword [en]
heterogeneous catalysis, anisotropic particles, protein gradients, nanoparticles
National Category
Chemical Sciences
Research subject
Organic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-88215ISBN: 978-91-7447-656-9 (print)OAI: oai:DiVA.org:su-88215DiVA: diva2:610745
Public defence
2013-04-18, Magnelisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of doctoral defence the following paper were unpublished and had a status as follows: Paper1: Manuscript; Paper 4: Manuscript

Available from: 2013-03-26 Created: 2013-03-11 Last updated: 2017-10-11Bibliographically approved
List of papers
1. Performance of a biomimetic oxidation catalyst immobilized on silicon wafers: comparison with its gold congener
Open this publication in new window or tab >>Performance of a biomimetic oxidation catalyst immobilized on silicon wafers: comparison with its gold congener
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2010 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 21, 16349-16354 p.Article in journal (Refereed) Published
Abstract [en]

With the aim of extending the usefulness of an existing biomimetic catalytic system, cobalt porphyrin catalytic units with thiol linkers were heterogenized via chemical grafting to silicon wafers and utilized for the catalytic oxidation of hydroquinone to p-benzoquinone. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to analyze the morphology and composition of the heterogeneous catalyst. The results of the catalytic oxidation of hydroquinone obtained with porphyrins grafted on silicon were compared with those obtained earlier with the same catalyst in homogeneous phase and immobilized on gold. It was found that the catalysis could run over 400 h, without showing any sign of deactivation. The measured catalytic activity is at least 10 times higher than that measured under homogeneous conditions, but also 10 times lower than that observed with the catalytic unit immobilized on gold. The reasons of this discrepancy are discussed in term of substrate influence and overlayer organization. The silicon-immobilized catalyst has potential as an advanced functional material with applications in oxidative heterogeneous catalysis of organic reactions, as it combines long-term relatively high activity with low cost.

National Category
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-45767 (URN)10.1021/la101631m (DOI)000283519300024 ()
Available from: 2010-11-11 Created: 2010-11-11 Last updated: 2017-12-12Bibliographically approved
2. Performance of a biomimetic oxidation catalyst immobilized on silica particles
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2013 (English)In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 303, 16-21 p.Article in journal (Refereed) Published
Abstract [en]

A biomimetic oxidation catalyst, cobalt porphyrin with thiol linkers, was chemically conjugated to silica particles and utilized in the oxidation of hydroquinone to benzoquinone. The cobalt porphyrin/silica particle catalyst was characterized with Inductively Coupled Plasma (ICP) and X-ray Photoelectron Spectroscopy (XPS). The catalytic performance of the cobalt porphyrin molecules was compared to previous results for the same catalyst grafted to a gold surface and on silicon wafers. The measured catalytic activity, after background correction, was 100 times higher than that of its homogeneous counterpart, 10 times higher than that on a silicon wafer, and almost the same as that on a gold surface. The turnover frequency rates after 400 h are still comparable with initial rates reported for homogeneous porphyrins and salophens, whereas the use of particles as support increases the active surface area, which removes the limitations for scale-up associated with the previously used silicon wafers and gold surfaces.

Keyword
Biomimetic, Catalysis, Cobalt porphyrin, Immobilization, Silica particles, X-ray Photoelectron Spectroscopy, Magnetic particles, Turnover number, Turnover frequency
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-92259 (URN)10.1016/j.jcat.2013.03.008 (DOI)000320216600003 ()
Funder
EU, European Research Council, AdG 247014Berzelii Centre EXSELENTSwedish Research Council
Note

AuthorCount:5;

Available from: 2013-07-25 Created: 2013-07-25 Last updated: 2017-10-11Bibliographically approved
3. Manufacturing of Anisotropic Particles by Site Specific Oxidation of Thiols
Open this publication in new window or tab >>Manufacturing of Anisotropic Particles by Site Specific Oxidation of Thiols
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2012 (English)In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 22, no 16, 7681-7683 p.Article in journal (Refereed) Published
Abstract [en]

A novel method for the manufacturing of functional anisotropic particles based on an inexpensive and straightforward electrochemical approach is presented. The method enables large-scale manufacturing of anisotropic particles as well as fabrication of multifunctional beads which may be used in the design of barcodes for multiplex diagnostics.

National Category
Natural Sciences
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-88206 (URN)10.1039/C2JM30475A (DOI)000302026100005 ()
Available from: 2013-03-11 Created: 2013-03-11 Last updated: 2017-12-06Bibliographically approved
4.
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5. Electrochemical Preparation of Dispersed Gold Nanoparticles Supported in the Pores of Siliceous Mesocellular Foam: An Efficient Catalyst for Cycloisomerization of 4-Alkynoic Acids to Lactones
Open this publication in new window or tab >>Electrochemical Preparation of Dispersed Gold Nanoparticles Supported in the Pores of Siliceous Mesocellular Foam: An Efficient Catalyst for Cycloisomerization of 4-Alkynoic Acids to Lactones
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

A versatile approach for the production of dispersed thiol-stabilized gold nanoparticles in the pores of siliceous mesocellular foam (MCF) is described and the thiol-stabilized gold nanoparticles were found to catalyze the cyclization of 4-pentynoic acids to lactones. The reported method is based on an electrochemical oxidation of a gold substrate generating oxidative Au(III) species which give rise to a surface-confined redox reaction yielding MCF supported Au(I)-thiolates. By reducing the MCF-S-Au(I) complex with sodium borohydride thiol-stabilized gold nanoparticles were obtained which were characterized with Transmission Electron Microscopy (TEM). The nanoparticles were found to be in the size of 1-8 nm. Inductive Coupled Plasma (ICP) analysis indicated an Au loading of 3 % (w/w) on the MCF. Further 0.5 mol% of the MCF-S-Au(0) solids were used to catalyze the cyclization reaction of 4-alkynoic acid under mild conditions with high selectivity (> 99%).

National Category
Natural Sciences
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-88208 (URN)
Available from: 2013-03-11 Created: 2013-03-11 Last updated: 2013-03-19Bibliographically approved
6.
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